Conventionally, in a lithography process for manufacturing a semiconductor device, a liquid crystal display device or the like, exposure apparatus such as a reduction projection exposure apparatus by a step-and-repeat method (the so-called stepper) or a scanning projection exposure apparatus by a step-and-scan method (the so-called scanning stepper (also called a scanner)) are relatively frequently used.
With these types of exposure apparatus, in order to transfer a pattern of a reticle serving as a mask onto a plurality of shot areas on a wafer, a wafer stage is driven, for example, by a drive unit including a linear motor or the like in an XY two-dimensional direction. The reaction force generated by the drive of the wafer stage was treated by mechanically releasing the reaction force to the floor (ground), using a frame member arranged at a datum (such as a base plate which is a reference point of the floor surface or the apparatus) which is insulated from vibration from the stage (for example, refer to Patent Document 1). Besides such treatment, in order to absorb the reaction force generated by the drive of the reticle stage in the scanning stepper, there were cases where a counter mass mechanism was employed that mainly used the law of conservation of momentum uniaxially in the scanning direction (for example, refer to Patent Document 2 below).
However, from the level required in fine processing, the reaction force released at the datum gave vibration to the projection optical system or to the stage to no small extent, and especially in the scanning stepper that performs scanning exposure while scanning the stage (or consequently, the wafer or the reticle), the vibration caused by the reaction force was a factor that caused a decrease in the exposure accuracy.
Further, transmission of the reaction force can be prevented almost completely in the case when the reaction force is absorbed using the counter mass mechanism; however, in the conventional counter mass mechanism, because a counter mass was used that moves in a direction opposite to the drive direction of the stage by a distance proportional to the driving distance of the stage, strokes corresponding to all the strokes of the stage had to be prepared also for the counter mass, which led to an increase in the size of the exposure apparatus.
Under such circumstances, with the aim of performing exposure with good accuracy and suppressing the increase in the size of the apparatus, the applicant had made a proposal earlier of an exposure apparatus that is equipped with a counter stage which moves in an opposite direction of a stage that holds an object according to the movement of the stage and a correction unit which has at least a part of the unit connected to the counter stage and corrects the position of the counter stage when an exposure beam is not irradiated (refer to Patent Document 3).
However, in the exposure apparatus disclosed in Patent Document 3 referred to above, because free motion of the counter stage was allowed according to the law of conservation of momentum in response to the movement of the stage and the position of the counter stage was corrected with the correction unit at an appropriate timing after the movement, a stage with a mass larger than that of the stage had to be employed as the counter stage in order to keep the movement stroke range of the counter stage from increasing unnecessarily. Especially in the case of a dual axis stage shaped in the letter H, as is disclosed in FIG. 2 of Patent Document 3 or the like, the stroke range of a stator (the counter stage) that constitutes a linear motor with a mover on the wafer stage side is preferably small, which meant that the mass of the stator (the counter stage) had to be large to some extent. Accordingly, in the current situation, it is not necessarily the case that the size of the apparatus is small enough to satisfy a sufficient level.
Patent Document 1: U.S. Pat. No. 5,528,118 description,
Patent Document 2: U.S. Pat. No. 6,255,796 description, and
Patent Document 3: U.S. Patent Application Publication No. 2004/0012768 description.